1. Field of the Invention
This invention relates to tamper indicators, and more particularly, to tamper indicators which function in response to relative movement between two separate elements of the indicator.
2. Description of the Prior Art
A wide variety of tamper indicators have been developed in the past primarily for application to medication containers including a cap. U.S. Pat. No. 4,424,911 (Resnick) discloses a tamper indicator for medicine bottles which changes color upon the application of pressure to the bottle during opening. A pliable strip is affixed to the exterior of the medication container. The strip contains fragible microspheres which, upon application of pressure caused by opening the container, changes the color of the strip.
U.S. Pat. No. 4,446,979 (Gach et al.) discloses a tamper indicating container having a two section cap. Relative rotation of the two cap sections during container opening displaces an "opened" sign into view on the top of the cap.
U.S. Pat. No. 4,448,317 (Thompson) discloses a tamper indicator for a container which includes a color change mechanism implemented by stress whitening or by an encapsulated coloring agent incorporated into a matrix. The color change is produced as a result of cap rotation.
U.S. Pat. No. 4,475,661 (Griffin) discloses a tamper indicating container having a transparent window in the cap. The indicator assembly includes a defaceable visual pattern such that movement of the cap relative to the receptacle defaces a visual pattern which becomes viewable through the cap.
U.S. Pat. No. 4,500,005 (Forrester) discloses a tamper-evident cap assembly for a container which includes a two-section rotatable bottle cap. Initial opening of the cap rotates one cap section with respect to the second cap section and moves the word "open" into view through an aperture in the top of the cap.
U.S. Pat. No. 4,502,605 (Wloszczyna) discloses a container closure identity system including two cap sections rotatable with respect to each other. One cap section contains dye while the other cap section contains an absorbent sheet together with an actuator. A transparent window in the cap permits the user to observe the color change caused by relative rotation of the two cap sections during opening of the container.
U.S. Pat. No. 4,436,213 (Paul, Jr. et al.) discloses a container having a tamper-evident seal. This device includes a transparent polymer film capable of being rendered transparent by the application of pressure to the film. A safety symbol is visible only if the container has not been previously opened.
U.S. Pat. No. 4,505,399 (Weiner) discloses a tamper-indicating device utilizing a light or oxygen responsive sheet which changes appearance irreversibly upon exposure to either light or oxygen.
U.S. Pat. No. 4,519,515 (Schonberger) discloses a tamper-evident lid for a container including a disc which is seated at the top of a bottle neck. The disc is coated with dye-filled micro capsules. The lower surface of the lid includes an abrasive material which ruptures the micro capsules when the lid is rotated to open the container.
U.S. Pat. No. 4,526,752 (Perlman et al.) discloses an oxygen indicator for packaging where the indicator changes condition upon exposure to oxygen.
U.S. Pat. No. 4,588,098 (Uzdy) discloses an enclosure having tamper indicating means including an indicator marker/pointer which moves in response to opening of the bottle and cannot be returned. This device includes a two-section cap having an upper part which rotates with respect to a lower part upon initial bottle opening.
U.S. Pat. No. 4,591,062 (Sandhaus) discloses a tamper-evident closure apparatus which includes a closure with a mechanism for venting internal pressurized gas upon unsealing of the container. In response to discharge of pressurized gas through a vent, indicator means changes color or is changed in physical shape to indicate tampering.